Femoral fixation

ABSTRACT

Various methods and devices are provided for a graft fixation device for fixing a graft member within a bone tunnel. In one embodiment, a graft fixation device is provided having a radially expandable sheath adapted to be disposed within a bone tunnel, and a sheath expander adapted to be received within the radially expandable sheath to expand the sheath and thereby anchor a graft between the sheath and the bone tunnel. In an exemplary embodiment, the graft fixation device is particularly useful to affix a graft within a femoral tunnel.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/996,384, filed Jan. 15, 2016, and entitled “FEMORALFIXATION,” which is a continuation of U.S. patent application Ser. No.14/268,538 (now U.S. Pat. No. 9,265,602), filed May 2, 2014, andentitled “FEMORAL FIXATION,” which is a divisional of U.S. patentapplication Ser. No. 13/533,375 (now U.S. Pat. No. 8,747,470), filedJun. 26, 2012, and entitled “FEMORAL FIXATION,” which is a continuationof U.S. patent application Ser. No. 11/537,180 (now U.S. Pat. No.8,226,714), filed Sep. 29, 2006, and entitled “FEMORAL FIXATION,” eachof which are hereby incorporated by reference in their entireties.

BACKGROUND

Ligaments are tough bands of tissue which serve to connect the articularextremities of bones, or to support or retain organs in place within thebody. Ligaments are typically composed of coarse bundles of dense whitefibrous tissue which are disposed in a parallel or closely interlacedmanner, with the fibrous tissue being pliant and flexible, but notsignificantly extensible.

In many cases, ligaments are torn or ruptured as a result of accidentsor overexertion. Accordingly, various procedures have been developed torepair or replace such damaged ligaments. For example, in the humanknee, the anterior and posterior cruciate ligaments (i.e., the ACL andPCL) extend between the top end of the tibia and the bottom end of thefemur. The ACL and PCL cooperate, together with other ligaments and softtissue, to provide both static and dynamic stability to the knee. Often,the ACL is ruptured or torn as a result of, for example, asports-related injury. Consequently, various surgical procedures havebeen developed for reconstructing the ACL so as to restore normalfunction to the knee.

In many instances, the ACL may be reconstructed by replacing theruptured ACL with a graft ligament. More particularly, with suchprocedures, bone tunnels are typically formed in the top end of thetibia and the bottom end of the femur, with one end of the graftligament being positioned in the femoral tunnel and the other end of thegraft ligament being positioned in the tibial tunnel. The two ends ofthe graft ligament are anchored in place in various ways known in theart so that the graft ligament extends between the femur and the tibiain substantially the same way, and with substantially the same function,as the original ACL. This graft ligament then cooperates with thesurrounding anatomical structures so as to restore normal function tothe knee.

A number of devices are currently employed for anchoring graft ligamentsin the femur, including the use of crosspins, interference screws, andbuttons which seat against the cortex of the femur when tension isapplied to the graft ligament. A number of problems result from thesetechniques. For example, the button is placed deep within the femoraltunnel and away from the joint line, which can cause the graft to movein a side-to-side motion, i.e., to have a windshield wiper effect, andto cause tunnel widening, potentially leading to joint laxity. Othercommon problems involved in femoral fixation include slippage of thedevice within the femoral tunnel, slippage of the graft ligamentrelative to the device, or damage to the graft ligament resulting fromcontact with the device itself, such as the graft ligament beinglacerated or wound up causing the graft orientation to be altered by thedevice.

Accordingly, there remains a need for a graft ligament anchor which issimple, easy to install, and inexpensive to manufacture, while providingsecure, trouble-free anchoring of the graft ligament.

SUMMARY

The present invention generally provides a methods and devices forfixing a graft member within a bone tunnel. In one embodiment, a graftfixation device is provided which includes a radially expandable sheathhaving proximal and distal ends with three sidewalls extendingtherebetween and defining a central lumen. The sheath can have asubstantially triangular cross-sectional shape. The graft fixationdevice also includes a sheath expander, for example, a tapered screw,adapted to be disposed in the central lumen of the radially expandablesheath and configured to flex the three sidewalls to radially expand thesheath so as to fix a graft member extending between the sheath and abone tunnel within the bone tunnel.

In one exemplary embodiment, the three sidewalls can be at leastpartially separated by three longitudinally oriented slots extendingtherebetween. For example, each sidewall can be connected by a proximalattachment point and a distal attachment point, with the slots extendingbetween the proximal and distal attachment points. In anotherembodiment, two of the sidewalls, e.g., the first and second sidewalls,can have a substantially concave outer surface adapted to seat a graftmember, and a third sidewall can have a substantially convex outersurface adapted to engage a bone tunnel. The sidewalls can also includeradially oriented ridges formed thereon.

The radially expandable sheath and sheath expander can also includeother features. For example, a proximal-most end of the radiallyexpandable sheath can be angled relative to a longitudinal axis of theradially expandable sheath. In another embodiment, the sheath expanderand a distal-most end of the radially expandable sheath each can includea lumen extending therethrough for receiving a guide wire. In otherembodiments, the radially expandable sheath can include a stop memberformed on a proximal end thereof and adapted to prevent over-insertionof the radially expandable sheath into a bone tunnel. The dimensions ofand materials used to form the expandable sheath and sheath expander canalso vary. Preferably, the sheath expander has a maximum outer diameterthat is greater than a maximum inner diameter of the radially expandablesheath in an unexpanded state, and the sheath expander and the radiallyexpandable sheath are formed from a biocompatible and/or bioabsorbablematerial. In another embodiment, the distal end of the expandable sheathcan include a cradle for seating the graft therein.

In another embodiment of the invention, a graft fixation device isprovided that includes an elongate expandable sheath having threesidewalls extending between proximal and distal ends. The threesidewalls can be attached to one another at a proximal attachment pointand a distal attachment point, and they can be separated from oneanother by three longitudinal slots extending between the proximal anddistal attachment points. The graft fixation device also includes anexpander disposable within the expandable sheath and adapted to expandthe sheath such that the proximal attachment points break to separatethe sidewalls at the proximal end of the sheath.

Exemplary methods for fixing a ligament graft in a bone tunnel are alsoprovided, and in one embodiment the method can include positioning aleading end of a graft within a femoral tunnel such that a trailing endof the grafts extends through a tibial tunnel. A flexible sheath can beinserted into the femoral tunnel, and it can have a substantiallytriangular cross-sectional shape such that flexible sheath positions thegraft on a posterior side of the femoral tunnel. The method can furtherinclude inserting an expansion plug into the flexible sheath to expandthe flexible sheath and thereby fix the leading end of the graft withinthe femoral tunnel. The method can also include inserting a graftfixation device into the tibial tunnel to fix the trailing end of thegraft within the tibial tunnel. The graft can include two or morebundles or strands, with each strand being looped at the leading end ofthe graft around a distal end of the flexible sheath. The flexiblesheath can include a cradle disposed on a distal end thereof forsecuring the strands at the leading end of the graft. In one exemplaryembodiment, positioning the leading end of the graft can include loopingthe leading end of the graft around a length of suture, and pulling thesuture through the tibial and femoral tunnels to pull the leading end ofthe graft into the femoral tunnel.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a side view of a radially expandable sheath and a sheathexpander in accordance with one embodiment of the invention;

FIG. 2 is a perspective view of the radially expandable sheath shown inFIG. 1

FIG. 3 is a side view of the radially expandable sheath shown in FIG. 1;

FIG. 4 is an end view of a distal end of the radially expandable sheathshown in FIG. 1;

FIG. 5 is a side view of a radially expandable sheath in accordance withanother exemplary embodiment of the invention having a feature disposedon the distal end of the sheath for seating a graft to prevent the graftfrom slipping;

FIG. 6 is a side view of a knee being prepared for the insertion of aradially expandable sheath and sheath expander, showing a guide pininserted through the knee;

FIG. 7 is a side view of the knee of FIG. 6, showing a reamer insertedover the guide pin;

FIG. 8 is a top view of the knee of FIG. 7, showing a passing pin aboutto be inserted into a socket formed in the femur;

FIG. 9 is a front view of the knee of FIG. 8, showing a graft insertedthrough femoral and tibial tunnels;

FIG. 10 is a side view of the knee of FIG. 9, showing a radiallyexpandable sheath being advanced into the socket formed in the femur;

FIG. 11 is a cross-sectional view of the femur of the knee of FIG. 10,showing the radially expandable sheath with a sheath expander disposedtherein; and

FIG. 12 is an end view of the proximal end of the radially expandablesheath disposed within the femoral tunnel of the knee of FIG. 11.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the devices andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

Various exemplary methods and devices are provided for fixing a graftmember in a bone tunnel. In general, a graft fixation device is providedhaving an expandable sheath with a central lumen formed therethrough,and a sheath expander that is adapted to expand the expandable sheath tofix a graft member within a bone tunnel. While the device can be used tofix a graft member within any bone, in an exemplary embodiment thedevice is adapted for use in the femoral tunnel. The device can thusinclude certain features to facilitate positioning of the graft at alocation that will reduce the risk of damage to the graft, as well asother features to facilitate femoral fixation. In one exemplaryembodiment, the device is configured to facilitate positioning ofindividual anteromedial and posterolateral bundles of a graft at alocation which corresponds to the position of anteromedial andposterolateral bundles of a natural ligament. A person skilled in theart will appreciate that the term “graft member” as used herein isintended to encompass a variety of materials, such as natural ligamentsand tendons, synthetic grafts and tendons, sutures, or any othermaterial that needs to be anchored within a bone tunnel. The variouscomponents of the device can also be formed from a variety of materials,but in an exemplary embodiment the expandable sheath and sheath expanderare formed from a biocompatible material. The components can also beformed from a bioabsorbable, biocompatible material, such as polylacticacid (PLA). However, it is understood that other suitable biocompatibleand optionally bioabsorbable polymers can also be used.

FIGS. 1-5 illustrate one exemplary embodiment of a graft fixationdevice. As shown, the graft fixation device 10 generally includes aradially expandable sheath 12 for attaching a ligament graft to bone,and a sheath expander 14 that is adapted to be disposed in a centrallumen of the radially expandable sheath 12 and that is configured toradially expand the sheath 12 so as to fix a graft member within a bonetunnel.

The expandable sheath 12 can have any shape and size but it should beadapted to expand within a bone tunnel to attach a graft to bone. In theillustrated embodiment, shown in more detail in FIGS. 2-4, theexpandable sheath 12 has an elongate configuration with an inner lumenextending between a trailing proximal end 16 and a leading distal end 18thereof. While the cross-sectional shape of the sheath 12 can vary, inan exemplary embodiment, the sheath 12 has a substantially triangularcross-sectional shape defined by three sidewalls 20, 22, 24 extendingbetween the proximal and distal ends 16, 18 of the sheath 12. Eachsidewall 20, 22, 24 can taper from a proximal end 16 of the sheath 12 toa distal end 18 of the sheath 12 to form a sheath 12 having abullet-shaped profile. As a result, the proximal end 16 of the sheath 12defines the largest outer diameter D₁ of the sheath 12, and the distalend 18 defines the smallest outer diameter D₂ of the sheath 12, as shownin FIG. 1. The sheath 12 also includes an inner diameter x which is thelargest at its proximal end 16 and decreases towards its distal end 18.The proximal end 16 of the sheath 12 can optionally be angled, as shownin FIGS. 1 and 3, to match an opening of a bone tunnel. The proximal end16 of the sheath 12 can also optionally be flared and/or can include alead-in to facilitate insertion of a threaded expander screw therein.For example, an inner surface of a proximal end of one or more of thesidewalls 20, 22, 24 can include a conical taper formed thereon tofacilitate engagement of the expander screw 14 with one or more threadsformed in the sheath 12, as will be discussed in more detail below. FIG.3 illustrates a conical taper 21 formed in the proximal end of sidewall20.

Each sidewall 20, 22, 24 of the sheath 12 is preferably separated froman adjacent sidewall by a longitudinally oriented slot 26, 28, 30extending therebetween. Each slot 26, 28, 30 can have the same lengthls, or alternatively the length of each slot 26, 28, 30 can vary withrespect to one another. In an exemplary embodiment, each slot 26, 28, 30has the same length ls and originates at or adjacent to the proximal end16 of the sheath 12 and extends along a substantial length Ls of thesheath to allow the sidewalls to flex with respect to each other. Eachslot 26, 28, 30 preferably terminates at the same position P justproximal to the distal end 18 of the sheath 12 to provide a slot-freedistal tip. This termination point P defines the area at which eachsidewall 20, 22, 24 will bend during expansion of the sheath 12 by asheath expander 14. Thus, while the termination point P can vary, thedistance between the termination point P at the end of each slot 26, 28,30 and the distal end 18 of the sheath 12 should be sufficient toprovide structural integrity to the device such that the sidewalls 20,22, 24 do not break apart from one another or from the distal tip duringexpansion. The sidewalls 20, 22, 24 can also optionally be connected toone another at or adjacent to the proximal end 16 of the sheath 12. Inone exemplary embodiment, the connections between the sidewalls 20, 22,24 can split or break when the sheath expander 14 is inserted into thecentral lumen of the sheath 12.

Each sidewall 20, 22, 24 of the sheath 12 can also have a variety ofshapes and sizes. In an exemplary embodiment, each of the first andsecond sidewalls 20, 22 has a substantially concave outer surface thatis adapted to seat a graft, and the third sidewall 24 has asubstantially convex outer surface that is adapted to engage a bonetunnel. The concave surface of the first and second sidewalls 20, 22,and the convex surface of the third sidewall 24 preferably extend alongthe length ls of the sidewalls 20, 22, 24. The proximal-most portion ofeach sidewall 20, 22, 24, however, can include a flared region toprovide an enlarged opening to the central lumen to facilitate insertionof the sheath expander 14 therein. The first and second sidewalls 20, 22can also include one or more surface features formed thereon tofacilitate engagement of a graft 100 between the sidewalls 20, 22 andthe bone tunnel when the sheath is implanted, and the third sidewall 24can include one or more surface features formed thereon to facilitateengagement with the bone tunnel. The surface features can have a varietyof configurations, and can be formed on all or a portion of one or moreof the sidewalls 20, 22, 24. As shown in FIGS. 1-3, the surface featuresare formed from a series of transversely-oriented ridges 46, 48 formedalong a substantial portion of each sidewall 20, 22, 24. In other words,the ridges 46, 48 extend radially around the sheath 12. The ridges 46formed on the first and second sidewalls 20, 22 can be effective toengage or grip the graft 100 to prevent sliding movement of the graft100 with respect to the sheath 12, and the ridges 48 formed on the thirdsidewall 24 can be effective to engage the bone tunnel to preventmovement of the device 10 within the bone tunnel. In an exemplaryembodiment, the ridges 46 formed on the first and second sidewalls 20,22 are positioned in an opposite direction to the ridges 48 formed onthe third sidewall 24. In particular, the ridges 46 formed on the firstand second sidewalls 20, 22 can be angled and pointed toward the distalend 18 of the sheath 12 to prevent a graft from sliding proximally, andthe ridges 48 formed on the third sidewall 24 can be angled and pointedtoward the proximal end 16 of the sheath 12 to prevent the sheath 12from sliding proximally. A person skilled in the art will appreciatethat the sheath 12 can include a variety of different features tofacilitate engagement between the sheath 12 and the graft and the sheath12 and the bone tunnel. For example, as further shown in FIG. 2, thesheath can include an axial rib 47 extending between the proximal anddistal ends 16, 18 of the sheath 12. The axial rib 47 can help preventrotation of the sheath 12 within the bone tunnel.

One or more sidewalls can also optionally include a stop member adaptedto prevent over-insertion of the sheath 12 into a bone tunnel. While thestop member can have a variety of configurations, FIGS. 1-2 illustrateone exemplary embodiment of a stop member 36 formed on the proximal-mostend of the sheath 12, and in particular on one of the sidewalls, e.g.,sidewall 24. The stop member 36 can have a variety of configurations,but in the illustrated embodiment, the stop member 36 is in the form ofa tab-like protrusion that extends radially outward from the proximalend 16 of the sheath 12. As a result, the stop member 36 will abut theedge of a bone tunnel during insertion of the sheath 12 into the bonetunnel, thereby preventing over-insertion of the sheath 12.

The distal tip 49 of the sheath 12 can also have a variety ofconfigurations, shapes and sizes. Since the distal tip 49 connects thethree sidewalls 20, 22, 24 to one another to provide structuralintegrity to the sheath 12, the distal tip 49 is preferably slot-free,and also preferably does not include any surface features formedthereon. While the shape of the distal tip 49 can vary, the distal tippreferably originates adjacent to the termination point P of eachlongitudinal slot, and tapers toward the distal-most end of the sheath12. The distal tip 49 can optionally include a flattened distal-mostsurface (shown in FIG. 1) for seating a graft therearound. The edges(not shown) that connect to the flattened surface are preferably roundedto form a substantially conical distal tip 49. The distal tip 49 canalso optionally include a bore 45 (shown in FIG. 2) extending throughthe flattened surface for receiving a guide wire therethrough tofacilitate implantation of the device 10. A person skilled in the artwill appreciate that the distal tip 49 of the sheath 12 can havevirtually any shape and size, and can optionally be substantially openor closed.

In another embodiment, the distal tip 49 can include features to seat agraft to prevent the graft from slipping. For example, the distal tip 49can include a cradle 50 disposed on the distal end 18, as shown in FIG.5. The cradle 50 can include opposed longitudinally-oriented fingersformed on the distal end of the distal tip 49 and adapted to seat thegraft therebetween. Each of the two bundles which make up the graft canbe looped around one of the fingers to prevent the graft from slipping.A person skilled in the art will appreciate that the cradle 50 can havea variety of configurations for securing the graft at the distal tip ofthe expandable sheath 12, and that the distal tip 49 can have variousother configurations to seat a graft to prevent the graft from slipping.

Referring back to FIG. 1, a sheath expander 14 can be used to expand theexpandable sheath 12 once the sheath 12 is inserted into a bone tunnel.While the sheath expander 14 can have virtually any configuration, FIG.1 illustrates one exemplary embodiment of a sheath expander 14 in theform of a tapered screw. The screw 14 includes a proximal end 40defining the largest diameter d₁ of the screw, and a distal end 42defining the smallest diameter d₂ of the screw. Threads 44 are formedaround the screw and extend from the proximal end 40 to the distal end42. In use, the screw 14 is adapted to expand the expandable sheath 12,thus the largest diameter d₂ of the screw 14 is preferably larger thanthe largest inner diameter x (FIG. 1) of the sheath 12, and morepreferably it is at least as large as the largest outer diameter D₁ ofthe sheath 12. The screw 14 is disposed in the central lumen of theexpandable sheath 12 and is configured to flex the three sidewalls 20,22, 24 and break the connections between the sidewalls 20, 22, 24 at theproximal end 16 of the sheath 12 to radially expand the sheath 12 to fixthe graft within a bone tunnel. The expander screw 14 can also include asocket formed in the proximal end thereof for receiving a driver tool,such as a hex wrench, that is effective to drive the screw 14 into thesheath 12. The expander screw 14 can also include a lumen (not shown)extending therethrough for receiving a guide wire to facilitateinsertion of the screw 14 into the sheath 12. As previously stated, aperson skilled in the art will appreciate the sheath expander 14 canhave a variety of configurations, shapes, and sizes. A person skilled inthe art will appreciate that a variety of implants having virtually anyconfiguration can be used to expand the expandable sheath, and thatsheath expander is merely one embodiment of an implant that can be usedwith the expandable sheath.

The expandable sheath and sheath expander can be used in a variety ofmedical procedures, but they are preferably used to anchor ligamentswithin a bone tunnel. In an exemplary embodiment, the device is used forfemoral fixation of a ligament graft. FIGS. 6-12 illustrate oneexemplary method of ligament graft fixation. A person skilled in the artwill appreciate that various other techniques known in the art can beused to perform each of the various steps of the procedure. In general,a graft can be prepared from two graft strands that are folded over tocreated a right bundle and a left bundle (or an anteromedial bundle anda posterolateral bundle), with each bundle having a portion of bothgraft strands. A length of suture can be whip stitched to each graftportion. As shown in FIG. 6, the knee 102 is flexed and a guide pin 108is placed in the knee 102 and through the femoral cortex. In oneembodiment, the knee 102 is flexed to 110 degrees and the guide pin 108is drilled through the femur 104. A reamer 110 can be inserted over theguide pin 108, as shown in FIG. 7, in order to drill a tunnel or socketin the femur 104, after which the guide pin 108 and reamer 110 areremoved. As shown in FIG. 8, a passing pin 112 holding a loop of suture114 is placed through the socket formed in the femur 104. The other endof the suture loop 114 is then pulled through the tunnel formed in thetibia 106 using a hook (not shown). A graft 100 is then passed throughthe tunnel in the femur 104 by passing the sutures attached to the graft100 through the suture loop 114 and pulling the suture loop 114 and thepassing pin 112 through the femoral tunnel, as shown in FIG. 9.

While tensioning the graft 100, the expandable sheath 12 can be insertedinto the opening of the bone tunnel in femur 104, as shown in FIG. 10,preferably by sliding the sheath 12 along a guide wire extending throughthe tunnel. A mallet or other impacting device can be used to gentlyadvance the sheath 12 into the tunnel. The stop member, if provided,will abut the opening of the tunnel when the sheath 12 is fullyinserted. In this position, the graft bundle is preferably seated withinthe two sidewalls of the expandable sheath 12 that have concave outersurfaces, e.g., sidewalls 20, 22. A tool, such as a spatula, canoptionally be used to separate the graft bundles and position them asdesired relative to the sheath 12. The angled distal end of the sheath12 can also be aligned with the opening of the tunnel, such that noportion of the sheath 12, other the stop member, remains external to thetunnel.

The sheath expander 14, e.g., tapered expander screw, can then be slowlyinserted into the central lumen of the sheath 12, for example, using adriver tool, to expand the sidewalls 20, 22, 24 of the sheath 12. Theconical taper formed in the proximal end of each sidewall 20, 22, 24 ofthe sheath 12 can facilitate alignment and engagement of the threads onthe sheath expander 14 with the threads formed in the sheath 12. As thesheath expander 14 is driven into the sheath 12, the sidewalls 20, 22,24 of the sheath 12 will deform outward toward a circular geometry toconform with an outer diameter of the expander 14. As a result, theconcave sidewalls 20, 22 will compress the graft bundles against thebone tunnel wall, as shown in FIGS. 11-12. The ridges 48 formed on thesidewalls 20, 22 will engage the graft to prevent the graft from beingpulled out of the tunnel. The third sidewall 24 will be compressedagainst the bone tunnel wall to engage the wall. The ridges 48 formed onthe third sidewall 24 will help prevent the sheath 12 from being pulledout of the bone tunnel. Once the graft 100, the sheath 12, and thesheath expander 14 are positioned within the bone tunnel, the placementof the graft 100, as shown in FIG. 12, will secure the graft 100 withinthe femoral tunnel. The triangular orientation of the sheath 12 is alsoadvantageous in that it can be used to position the graft towards theposterior side of the tunnel, creating a fan-like orientation with thegraft strands. In this configuration, the graft strands mimics theposition of a natural graft. In particular, the triangular orientationof the sheath 12 causes the graft strands to be positioned at a locationin which a natural graft would normally be positioned, thus the graftstrands will mimic the function of a natural graft. During bending ofthe knee, the graft will extend over the anterior side Xa (FIG. 11) ofthe tunnel, and thus over the head of the sheath expander. Since thesheath 12 compresses the graft toward the posterior side Xp (FIG. 11) ofthe tunnel, the graft is prevented from rubbing against the anterioredge Xa of the bone tunnel, thereby reducing the risk of damage to thegraft. As noted above, this orientation also more closely mimics theanatomic footprint of the native ACL, adding rotational stability to thejoint.

In another embodiment, a kit may be provided to a surgeon that includesa variety of expandable sheaths and sheath expanders to accommodate avariety of procedures and graft sizes. For example, multiple sheathswith a variety of sizes, including sheaths of different lengths anddiameters, may be provided to be used with a variety of bone tunnels ofdifferent sizes. Multiple sheath expanders having different sizes mayalso be provided in the kit for use with a single size sheath toaccommodate different sized grafts.

One of ordinary skill in the art will appreciate further features andadvantages of the invention based on the above-described embodiments.Accordingly, the invention is not to be limited by what has beenparticularly shown and described, except as indicated by the appendedclaims. All publications and references cited herein are expresslyincorporated herein by reference in their entirety.

What is claimed is:
 1. A method for fixing a ligament graft in a bonetunnel, comprising: positioning a leading end of a graft within a bonetunnel, the graft having a trailing end that extends through a tibialtunnel; inserting a flexible sheath into the bone tunnel, the flexiblesheath having first, second, and third sidewalls that define an innerlumen extending through the flexible sheath, the flexible sheath havinga substantially triangular cross-sectional shape perpendicular to alongitudinal axis of the flexible sheath such that flexible sheathpositions the graft on a posterior side of the bone tunnel, the flexiblesheath having a stop member formed on a proximal-most end of the firstsidewall with a distal face of the stop member being distal to aproximal-most surface of the second and third sidewalls, and the stopmember abutting an edge of the bone tunnel during insertion to preventover-insertion of the flexible sheath, and the proximal-most end of theflexible sheath being angled to align with the edge of the bone tunnel;and inserting a screw into the flexible sheath to expand the flexiblesheath and thereby fix the leading end of the graft within the bonetunnel.
 2. The method of claim 1, wherein inserting the screw into theflexible sheath includes engagement of the screw with one or morethreads formed on an inner surface of the flexible sheath.
 3. The methodof claim 1, wherein inserting the screw into the flexible sheathincludes inserting the screw into the inner lumen.
 4. The method ofclaim 1, wherein expansion of the flexible sheath includes deformationof the first, second, and third sidewalls such that the substantiallytriangular cross-sectional shape of the flexible sheath changes to adifferent shape.
 5. The method of claim 4, wherein the different shapeconforms to a shape of an outer diameter of the screw.
 6. The method ofclaim 1, wherein the first, second, and third sidewalls are eachconnected by a proximal attachment point and a distal attachment point.7. The method of claim 1, wherein expansion of the flexible sheathincludes a substantially convex outer surface of the first sidewallengaging the bone tunnel.
 8. The method of claim 1, wherein expansion ofthe flexible sheath includes surface features formed on the second andthird sidewalls engaging the graft, and surface features formed on thefirst sidewall engaging bone within the bone tunnel.
 9. The method ofclaim 1, further comprising inserting a guide wire through the innerlumen of the flexible sheath.